Prior art driving systems, which form component of invalid chair and enable person operating the invalid chair to pass fly-over obstacles such as especially steps, have very complex and costly constructions completed with necessary electromotive drive and often even with computer regulating balance of invalid chair when passing the mentioned obstacles. In view of the fact that invalid chairs equipped with these systems for the most part are not reasonably priced for disabled persons, there is a demand at present for invalid chair that would have relatively simple construction that would enable person operating the invalid chair to bridge fly-over obstacles solely by exerting manpower. This demand is satisfied by driving system for passing fly-over obstacles by invalid chair according to the present invention.